1. Field of the Invention
The present invention relates to a digital camera having a live view display function, and to a control method for a digital camera, and in detail relates to a digital camera having a so-called Live View function (also called an Electronic Viewfinder Function) for displaying an image acquired by image sensors as a moving image on a display unit, and to a control method for such a camera.
2. Description of the Related Art
In a conventional digital camera, observation of a subject image is performed using an optical viewfinder. However, recent digital cameras utilize display of output of an image sensor, provided for storage of subject image data, either without an optical viewfinder or together with an optical viewfinder. Specifically, it has become common to have a live view function where an image acquired by an image sensor is displayed using a display device such as a liquid crystal monitor for observation of a subject image.
In the case of a digital camera having this type of live view display function, the amount of subject image data acquired by the image sensor increases, and further if the number of times the image sensor is read per unit time period is increased, the internal power consumption increases. As a means of dealing with this situation, a digital camera has been proposed, in Japanese patent laid-open No. 2004-15595 (laid-open Jan. 15, 2004) in which a frame rate is switched depending on an exposure mode, detected battery voltage, etc. Also, Japanese patent laid-open No. 2005-260733 (laid-open Sep. 22, 2005) discloses a digital camera in which, as a measure to deal with flicker caused at the frequency of the mains power supply, namely 50 Hz or 60 Hz, in a standby state image data is read from the image sensor at a high frame rate, and switched to a low frame rate when the release button is pressed down halfway.